Carbene-Anchored Boryl- and Stibanyl-Phosphaalkenes as Precursors for Bis-Phosphaalkenyl Dichlorogermane and Mixed-Valence Ag^I/Ag^IIPhosphinidenide

Abstract

Cyclic alkyl­(amino) carbene (cAAC)-anchored boryl- and stibanyl-phosphaalkenes with general formula cAAC = P–ER2 [E = B, R = (N i Pr2)2 (3a-c); E = Sb, R = 2,4,6-triisopropylphenyl (5a-b)] have been synthesized and utilized as precursors for the bis-phosphaalkenyl dichlorogermane [(cAAC = P)2GeCl2] (6) and the first molecular example of a neutral polymeric mixed-valence AgI/AgII phosphinidenide complex [(cAACP)2Ag4 IAgIICl4] n (7). All compounds have been characterized by single-crystal X-ray diffraction and further investigated by nuclear magnetic resonance (NMR), mass spectrometric analysis, and UV–vis/fluorescence measurements. The paramagnetic complex 7 has been characterized by ESR spectroscopy. Cyclic voltammetry studies of compounds 3/5 have suggested possible one-electron quasi-reversible reductions, indicating their redox noninnocent behavior in solution. Quantum chemical studies revealed the electron-sharing nature of the P–B and P–Sb σ bonds in compounds 3 and 5, and the polar CcAAC = P bonds in compounds 3, 5, and 6 prevailing their phosphaalkene structures over phosphinidenes.

Isolation of (Aryl)‐(Imino) Phosphide and (Aryl)‐(Phosphaalkene) Amide Complexes of Alkali Metals from Carbene‐Phosphinidenes under Reductive‐Thermal Rearrangements

“…The C cAAC −P bond consists of electron sharing covalent double bonds (σ, π; see the EDA‐NOCV analyses given in the Supporting Information). A similar bonding situation has been observed in the previously reported boryl‐ and stibanyl‐phosphaalkenes cAAC=P−ER 2 [E=B, Sb] [15] . N1 is bonded to two B(N i Pr 2 ) 2 groups.…”

“…The 31 P NMR spectra of C 6 D 6 solutions of pure crystals of 8 a – 8 c exhibited singlets at 35.1, 43.1, and 41.7 ppm (see the Supporting Information), respectively, which are very much downfield shifted when compared to those of the Cs complexes 3 a – 3 c (−55.5, −60.9, and −63.3 ppm, respectively); upfield shifted when compared to that of the chloro‐phosphinidenes 1 a – 1 c ; [8] and Cy‐cAAC‐phenyl‐phosphinidene (Cy‐cAAC)P−Ph [7] (68.9 ppm). The 11 B NMR spectra of C 6 D 6 solutions of 8 a – 8 c exhibited singlets at 29.8, 24.2, and 29.6 ppm (see the Supporting Information), respectively, which are upfield shifted when compared to those of the previously reported boryl‐phosphaalkenes [cAAC=P−B(N‐( i Pr) 2 ) 2 ] (40.8–42.1 ppm) [15] . The 13 C NMR spectra of C 6 D 6 solutions of 8 a – 8 c exhibited doublets corresponding to C cAAC at 206.3 ( J C−P =64.64 Hz), 204.7 ( J C−P =60.6 Hz), and 205.5 ( J C−P =60.6 Hz) ppm, respectively (see the Supporting Information), which are upfield shifted when compared to those of the chloro‐phosphinidenes 1 a – 1 c (208.2 ( 1 a ); 210.0 ( 1 b ), and 210.9 ( 1 c ) ppm, respectively), [8] and upfield shifted when compared to that of (Cy‐cAAC)P−Ph (208.1 ppm) [7] .…”

Isolation of Homo‐/Mixed‐Valence Ag12, Ag29, and Ag8Clusters Stabilized by Cyclic Alkyl(amino) Carbene‐Anchored Monoanionic Phosphorus Ligand

“…The cyclic alkyl(amino) carbene (cAAC)‐supported boryl‐phosphaalkene, (cAAC)P‐B(N i Pr 2 ) 2 (cAAC=:C(N‐2,6‐ i Pr 2 C 6 H 3 )(C 6 H 10 )(CMe 2 )(CH 2 )) [22] has been employed for the first time as the precursor for the in situ generation of (cAAC)P − under ambient reaction condition as a redox non‐innocent anion. The reaction of (cAAC)P − with AgOTf in 1 : 1 molar ratio at room temperature in anhydrous toluene for 12 h resulted in the formation of a brownish‐red reaction mixture with brown precipitate, which was isolated upon filtration, and dissolved further in anhydrous dichloromethane (DCM) to obtain a brownish‐red clear solution.…”

“…[19] Clusters of AgÀ H moieties have been isolated, [20] and their corresponding bare Ag n H + cations have been studied by mass spectrometry. [21] Using the unique electronic effects of cAAC and phosphorus, herein, we report on the first syntheses, isolation, and characterization of three air, and moisture sensitive, mixed-valence Ag The cyclic alkyl(amino) carbene (cAAC)-supported borylphosphaalkene, (cAAC)P-B(N i Pr 2 ) 2 (cAAC=:C(N-2,6-i Pr 2 C 6 H 3 )(C 6 H 10 )(CMe 2 )(CH 2 )) [22] has been employed for the first time as the precursor for the in situ generation of (cAAC)P À under ambient reaction condition as a redox non-innocent anion. The reaction of (cAAC)P À with AgOTf in 1 : 1 molar ratio at room temperature in anhydrous toluene for 12 h resulted in the formation of a brownish-red reaction mixture with brown precipitate, which was isolated upon filtration, and dissolved further in anhydrous dichloromethane (DCM) to obtain a brownish-red clear solution.…”

“…The formation of the byproduct (cAAC) 2 P 2 has been confirmed by NMR analysis. [15] To explore the role of the counter anion a different silver salt, viz, AgNTf 2 has been employed in the similar reaction with phosphaalkene ((cAAC)P-B(N i Pr 2 ) 2 ), [22] which could not produce any desired Ag cluster. However, a 1 : 1.5 molar ratio of the potassium phosphinidenide (cAACPK), and AgNTf 2 reacted in toluene at À 40 °C to room temperature, affording the greenishbrown colored residue after 12 h, which was filtered to give a reddish-brown filtrate, and dissolved further in anhydrous DCM Scheme 1.…”